Electrical initiator

ABSTRACT

An initiator having a body of nitrocellulose material having a surface characterized by thin fibres or thin webs with a film of a conductive material adhered to said surface.

States Patel 1 lrish, Jr. et a1.

[ Mar. 26, 1974 ELECTRICAL INlTIATOR [76] Inventors: Charles G. lrish,Jr., 49 Sylvan,

Cheshire, Conn. 06410; Joseph W. Silva, Foote Hill Rd., Northford, Conn.06472; Raymond I. Owles, Ansonia Rd., Woodbridge, Conn. 06525 [22]Filed: Sept. 5, 1972 [21] Appl. N0.: 286,388

Related US. Application Data [62] Division o f S er: fi'o. i;4s0,mf2"1,i'WOTaBZfiiidEd.

[52] US. Cl. 102/100, 102/103 [51] lnl. Cl. F42b 9/08 [58] Field ofSearch 102/99-104,

102/38, DIG. 1, 46

[56] References Cited UNITED STATES PATENTS 3,336,871 8/1967 Quinlan102/38 3,299,812 l/l967 Suh et a1 v 102/46 X 39,542 8/1863 Beardslee 1.102/46 X Primary ExaminerRobert F. Stahl Attorney, Agent, or Firm-DonaldR, Motsko; H. Samuel Kieser; William W. Jones [57] ABSTRACT An initiatorhaving a body of nitrocellulose material having a surface characterizedby thin fibres or thin webs with a film of a conductive material adheredto said surface.

2 Claims, 7 Drawing Figures ELECTRICAL INITIATOR This is a division ofapplication Ser. No. 04,480, filed Jan. 21, 1970 now abandoned.

This invention relates generally to the field of initiators. Moreparticularly, this invention relates to an initiator of a smokelesspropellant which is capable of being electrically ignited.

An initiator is the first element in a device using explosive,propellant, or pyrotechnic materials, The initiator responds to an inputstimulus and starts the burning or explosive reaction. lnitiators areclassified according to the nature of the input stimulus which can beeither mechanical or electrical. lnitiators may be further classifiedaccording to their intended output function as primers, "sq uibs, ordetonators. As will be" disclosed, this invention concerns an initiatorwhich responds to an electrical input impetus and whose outputcharacteristics are such as to enable it to act as a primer, a squib, orthe first element of a detonator.

Electric initiators may be further categorized by the type of transducerused to convert the electrical input energy into heat energy.Transducers that may be used with electrical initiators include a hotbridgewire or an exploding bridgewire, a conductive mix, a conductivefilm bridge, and a spark gap. The input sensitivity varies sharply withthe type of transducer; each type having a characteristic thresholdfiring energy and current requirements. This invention concerns thattype of electric initiator wherein the transducer is a conductive filmbridge.

It is thought that an understanding of the nature, construction, andelectrical input characteristics of a conductive film bridge initiatorwhich existed prior to this invention would be helpful in understandingthe present invention. Conductive films may be applied to the surface ofinsulators by a variety of techniques to produce bridges which can beheated or exploded to initiate explosive reactions. The only type offilm bridge applied in standard fuzes has been the low-energy graphiteor carbon bridge. These bridges are all made by essentially the sameprocess. A droplet of a colloidal suspension of graphite in water isdeposited on a surface which consists of two or more metal electrodesseparated by, and usually imbedded in, an insulator. Because graphitehas a negative resistance temperature coefficient and because of theinherent variable film thickness and path length, the electric currentis channeled into a path which is only a small part of the total volumeof the film. Only this small portion of the film is heated.Characteristically, the resistance spread is very wide ranging from 700to 14,000 ohms. Because of thechanneled path, the energy required forignition is low, in the order of only a few hundred ergs. As a furtherconsequence of the channeled path, the mass of graphite heated is small.To be effective as an ignitor, this small mass of graphite must be inintimate contact with a primary explosive which is thermally sensitiveand has good propagation characteristics. The primary explosives, leadazide and lead styphnate, are universally used as spotting charges notonly for graphite or carbon bridge devices but also for every type ofpresent initiator except the exploding bridgewire whose greater energyrelease permits the use of secondary explosives under special conditionsof particle size and confinement.

We may summarize the salient characteristics of currently employedconductive film initiators as follows:

1. The conductive film may be metallic or nonmetallic but non-metalliccarbonaceous materials are most usual.

2. The carbonaceous film bridge is electrically characterized by a highresistance of 700 to 14,000 ohms and is very sensitive to electricenergy input requiring, at the most, a few hundred ergs for initiation.

3. All present conductive film bridge initiators require the presence ofa primary explosive, commonly lead styphnate or lead azide, in directand intimate contact with the bridge.

4. Generally,'the conductive film bridge is applied to the surface of aninsulating material into which are imbedded two or more electrodes.

The critical dimensions, the non-uniformity, and, above all, thesusceptibility of the low-energy carbon bridge to accidental discharge,as, for example, by the static electricity accumulated on a person, orthat induced by radio frequency or radar energy sharply limit the usesof the carbon bridge conductive film device and it is found thatbridgewire devices are almost universally used to fulfill the presentday needs for electric initiators.

The bridgewire initiator requires an assembly which is relativelycomplex and costly. Further (except in the special case of the explodingbridgewire) it universally requires the presence of a primary explosiveto be in intimate contact with the wire to act as the initiator for whatis usual train of several explosive materials.

In view of the above, it is an object of the present invention toprovide an electric initiator that does not require the presence of aprimary explosive material.

A further object of the present invention is to provide an electricinitiator of the conductive film type which possesses the electrical andsafety characteristics of the bridgewire type without the attendantcomplexity and high cost.

Yet another object of the present invention is the provision of anelectric initiator which does not require a primary explosive and whichmay be used by itself as a source of power to drive projectiles, bolts,studs or the like, or which can be used as a means for ignitingadditional powder, pyrotechnic material or as the first element in atrain of explosives.

Generally, the initiator of the present invention comprises a body ofnitrocellulose material having a surface characterized by thin fibresor, alternately, thin webs with a thin film of a semi-conductivematerial adhered to said surface.

The objects and advantages of the present invention will become moreapparent by reference to the following description of several preferredembodiments and to the accompanying drawing in which:

FIG. 1 is a cross-sectional view of an initiator constructed inaccordance with the present invention;

FIG. 2 is a cross-sectional view of one embodiment of a shotshellincorporating the initiator of the present invention;

FIG. 3 is a cross-sectional view of a second embodiment of a shotshellincorporating the initiator of the present invention;

FIG. 4 is a corss-sectional view showing a projectile attached to theinitiator of the present invention;

FIG. 5 is a sectional view showing the initiator used in conjunctionwith caseless ammunition;-

FIG. 6 is a cross-sectional view showing the initiator used in anindustrial type fastening tool; and

FIG. 7 is a schematic diagram of an electrical circuit which may be usedto supply the power for the initiator.

Referring to the drawings, and in particular FIG. 1, the initiator 2 ofthe present invention includes a body 4 of either fibrous or porousnitrocellulosehaving a surface characterized by either thin fibres orthin webs of nitrocellulose. A thin film 6 of a semi-conductive,nonmetallic material is adhered to the surface with the thin fibres orthin webs being intimately coated with the conductive material.

In practicing the present invention, any nitrocellulose may be usedwhich when formed into its desired shape will have a fibrous, stringy,or porous structure, such that the overall density of the nitrocellulosebody will be between about 0.85 and 1.40 grams per cubic centimeter. Thereceptive surface of such a body to which the conductive film is appliedis characterized by having either exposed thin fibres or exposed thinwebs of nitrocellulose which are intimately coated with the conductivematerial. It is these thin fibres and thin webs of nitrocellulose whichare readily heated to their ignition point by the transfer of heat fromthe conductive film as the film is heated by the applied electricalenergy.

One type of material ideally suited for the purposes of this inventionis bulk powder as is fully described in U.S. Pat. No. 3,463,086. Thispowder is characterized as being fibrous, stringy, or fuzzy and may becompacted in the dry state to form pellets, grains, charges or shapeswhich faithfully retain the form into which they are compacted and whoseignition and combustion characteristics may be varied. This type ofpowder, when compacted, will have a surface which includes exposed thinfibres which can be intimately coated with the conductive material.

However, other means are available of attaining the proper receptivesurface. Fibrous, non-gelatinized, virgin nitrocellulose may be used.The sponge-like irregular particles of precipitated nitrocelluloseprovide exposed thin fibres on the surface which is receptive to theconductive coating. Preferably, precipitated nitrocellulose may be madeby first dissolving nitrocellulose in a solvent such as acetone to forma lacquer and then pouring the lacquer into an excess of water undervigorous agitation. Under this treatment the nitrocellulose precipitatesout as solid particles which, under microscopic examination, are ofirregular shape and of sponge-like character.

In addition, nitrocellulose prepared by the wash out process may beutilized in the forming of the body 4 of the initiator 2. In thisprocess, nitrocellulose together with a stabilizer and a suitablewater-soluble salt is gelatinized with a solvent, extruded or moldedinto a pellet shape, extracted with hot water to remove thewater-soluble salt and dried. A homogeneous structure results which,under microscopic examination, resembles a slice of bread, i.e.irregular pores formed by relatively thin webs. An additional method ofproviding a receptive surface on a nitrocellulose body which isotherwise fully gelatinized, is by mechanically abrading or scoring thesurface or by treating the surface with a solvent.

The conductive film 6 which is applied to the nitrocellulose 4 is formedfrom a material of moderate electrical resistivity which also has anegative temperature coefficient of electrical resistivity. Ofparticular value because of their ready availability and low cost aregraphite, partially graphitized carbon black, and finely divided leadperoxide. Other materials which might be employed would include the moreexotic semiconductors such as germanium and silicon which also have anegative temperature coefficient of electrical resistivity.

The preferred materials for the present invention are graphite,graphitized carbon black and lead peroxide. These are preferably appliedas colloidal or semicolloidal suspensions in an aqueous or non-aqueousmedia together with suitable organic or non-organic binders. These areapplied in a manner such that the dried, adherent film has a thicknesswhich may be varied from 0.5 mil to 2.0 mils and may, with the electrodeemployed, show resistance from about 2 ohms to about ohms with the rangeof 5 ohms to 20 ohms being preferred.

If desired, an oxidizing material may be incorporated into theconductive film 6 or into the receptive surface of the nitrocellulosebody to enhance the ignition. Suitable oxidizers include the nitrates,chromates and dichromates of barium, potassium and sodium, the peroxidesof barium and strontium, the chlorates, perchlorates and sulfates ofpotassium, and the oxides and peroxides of lead.

The initiator 2, either alone or supplemented by additional propellant,may be used as a source of power to drive projectiles, bolts, studs,nails, etc. It may also be used as a power capsule to start a smallgasoline engine or the like or it may be used as a means of igniting alarger propellant mass, a mass of pyrotechnic composition or as thefirst element in a tain of explosives. FIGS. 2-6 depict various ways ofutilizing the initiator of the present invention.

In FIG. 2, a standard shotshell 8 comprises a plastic v body 10 having ahead portion 12 and open cavity 14.

Within the cavity 14 is placed a propellant charge 16 of suitablecomposition. A cup wad l8 and fibrous wad 20 overlie the power charge 16in a manner well known in the art. The remainder of the cavity 14 isfilled with shot 22 and the end of the tube (not shown) closed in anyconventional manner. A metallic head 24 overlies the plastic head 12 ofthe shotshell and has a portion 26 inturned into the primer orifice 28.A battery cup 30 extends through the primer orifice 29 and communicateswith the powder charge 16. The initiator 2 is mounted in the battery cup30 in a position adjacent to propellant charge 16. The conductive film 6of the initiator 2 is in contact with an electrode structure 32 mountedin the rearward end of the battery cup 30. The electrode structure 32includes a hollow, cylindrical band 34 of conductive material which isin electrical contact with the battery cup 30 and a central electrode 36of suitable conductive material separated from the outer electrode 34 bysuitable insulating material 40. This type of shotshell maybe mounted ina cartrige chamber of a firearm having a breech 42 provided with asuitable electrode which comprises an outer electrode 44 generallycirculr in transverse crosssection which is adapted to be placed inelectrical contact with the metallic head 26 and a central electrode 46which is adapted to engage the central electrode 46 of the electrodestructure 32. The electrodes 44 and 46 are separated from each other bymeans of suitable insulation 48. It is to be understood that the batterycup 30 with the initiatoe 2 and electrode structure 32 could also beused in place of the percussion primer normally used in conventionalrifle and pistol ammunition to fire a single projectile.

In FIG. 3, a second embodiment of a shotshell 50 is shown which includesas in FIG. 2, a plastic case having a head portion 12 and suitablewadding l8 and 20. A suitable amount of shot 22 is provided in theforward end of the shell. Immediately below the wadding 18 is placed acompacted or bonded pellet 52 formed of an appropriate smokeless powder.A hollow S4 is formed in the rearward end of the pellet 52 and aninitiator 2 inserted into the pellet with the conductive film 6 facingthe opening in which the primer would normally be inserted. With thisparticular shotshell, the use of a metallic head 24 is optional. Theshotshell 50 is adapted to be placed in the cartridge ofa firearm whichis equipped with an electrode probe 56 adapted to extend through theprimer opening into intimate contact with the conductive film 6 of theinitiator 2. The electrode 56 may take the form of a hollow,cylindrical, outer electrode member 58 and a central rod-like electrode60 spaced from the outer electrode 58 by suitable insulation 62. It isto be noted that as in the modification shown in FIG. 2, themodification of FIG. 3 could be used in connection with centerfire rifleammunition to propel a bullet. As another alternative, instead of theadditional powder being in the form of a pellet 52, it is possible toform such powder as part of the initiator body 2 whereupon theconductive film 6 would simply be of such a size as to insure that itwould come into intimate contact with the electrode.

FIG. 4 shows the use of the initiator 2 as a propellant for ammunition.In this particular case, the initiator body 4 is in the form of apellet. One surface of the pellet is attached to a bullet 64 bymechanical means, by adhesives or in a number of other ways well knownto those skilled in the art. The opposite surface of the initiator body4 contains the conductive film 6 as heretofore described.

FIG. 5 shows yet another form of caseless ammunition in which theinitiator 2 of the present invention may be utilized. A generallycylindrical, hollow, molded propellant body 66 may be provided asmentioned in US. Pat. No. 3,311,057. The usual projectile 68 may beadhesively or otherwise secured in the forward end of the propellantbody 66 and an initiator 2 of the present invention secured within therearward end of the body 66 with the conductive film 6 being exposed forcontact with the electrode structure of an appropriate firearm.

TABLE I Capacitance Voltage for 99.95 Energy for 99.95 Probability toProbability to Fire Fire 30 microfarads 25! volts 0.94 joules I20 llOvolts 0.73 joules 480 57 volts 0.77 joules The following examples areintended to illustrate some of the many uses to which the initiator 2 ofthe present invention may be put as well as illustrate the variousparameters used for its successful functioning.

EXAMPLE I Pellets of propellant were made by compacting dense bulkpowder to a diameter of about 0.650 inch and a thickness of about 0.250inch. The pellets weighed be tween about 20 to 24 grains and had adensity of about 1.3 grams per cubic centimeter. On one of the flatfaces of each pellet a drop of a diluted suspension of colloidalgraphite in water was placed. The graphite suspension was oven-dried fortwo hours at F. A portion of the graphite suspension permeated betweenand adhered to the exposed fibres of the pellets. The remainder of thegraphite suspension formed a film on the surface of the pellets. Thefilms had a thickness of between about 0.5 to 1.0 mil. With concentricelectrodes having a center conductor'of0.040 inch outer diameter and aninsulation thickness between the inner and outer electrodes of about0.040 inch, the films displayed an individual resistance ranging fromabout 3 ohms to I00 ohms with a predominating majority being between 5ohms and 15 ohms. Each pellet was placed in the end of a shotshell inplace of the regular powder charge and primer. The shotshells wereprovided with conventional type wadding and shot pellets. The shotshellswere placed into a test vehicle for firing which included abatterycapacitor circuit with suitable switching to permit the chargingof the capacitor from the battery and, susequently, the discharge of thecapacitor through the electrode which was placed in firm contact withthe conductive film on the pellet. The capacitor, having a capacitanceof 480 uF, was charged to a voltage of 65 volts. Thus the energy in thepower supply was equal to l joule. The pellets ignited within a periodof l to 2 milliseconds after application of the electrical energy andburned as a propellant yielding the pressure and velocitycharacteristics normally expected in a shotshell. In the case ofgraphite films having a thickness of 0.5 mil, a burn out of theconductive film occurred before the energy was drained from thecapacitor. In these instances, the actual energy consumed for ignitionwas of the order of 0.2 to 0.5 joule.

EXAMPLE II In a manner similar to Example I, an ignition pellet was drycompacted from bulk powder to a density of about 1.2 grams per cubiccentimeter and a diameter and thickness of about 0.2 inch. One face ofthe pellet was coated with a graphite film as explained in connectionwith Example I. The electrode employed had a gap dimension of about0.020 inch. The pellet was placed in a suitable text fixture for firinga 0.22 caliber rifle bullet. Utilizing the power supply of Example, I,the pellet ignited and burned yielding the pressure and velocitycharacteristics normally expected from the firing of conventional 0.22caliber ammunition. The ignition delay after application of the energywas in the order of l to 2 milliseconds and the energy consumed lessthan 1 joule.

EXAMPLE III In manner similar to Examples I and II, an ignition pelletwas dry compacted from bulk powder to a density of about 1.2 grams percubic centimeter and a diameter of about 0.4 inch and a thickness ofabout 0.150 inch. One face of the pellet was coated with a graphite filmin a manner mentioned in connection with Example I. The pellet wasplaced in a test fixture resembling an industrial type powder-actuatedfastening tool of the piston type similar to that shown in FIG. 6.Onapplication of electrical energy by use of the circuit mentioned inExample I, the pellet ignited and burned and successfully drove thepiston which in turn drove the fastener into the work surface.

EXAMPLE IV An ignition pellet was compacted into the form of a waferfrom bulk powder to a density of 1.25 grams per cubic centimeter. Onesurface of the wafer was coated with an aqueous dispersion of graphiteas heretofore mentioned. A conventional shotshell was modified byremoving the primer and the ignition pellet was inserted into theopening leaving room for the insertion into the primer opening of anelectrode. Over the ignition pellet was placed a propellant charge ofconventional granular propellant and the shell charged normally withshot and wads, On application of about 1 joule of electrical energy, thepellet initiatedthe combustion of the granular propellant yieldingpressure and velocity characteristics normally associated with aconventional shotshell. I

EXAMPLE V A conventional shotshell was modified by substituting for thestandard percussion primer a battery cup closed at one end with theelectrode of Example I into which was pressed a cylindrical ignitionpellet of compacted bulk powder having a face coated with graphite filmin intimate contact with the electrode. This arrangement is depicted inFIG. 2 of the drawings. Upon the application of about I joule ofelectrical energy, the pellet initiated the combustion of the granularpropellant yielding expected pressure and velocity characteristicsnormal to shotshells.

EXAMPLE VI A densely colloided smokeless powder was formed into a pelletusing the wet solvent processtaught by US. Pat. No. 3,092,525. Aninitiator pellet of the type described in Example Ill was placed into asuitable hollow molded into the pellet. In this instance, the weight ofthe bulk powder initiator pellet was about 3 grains and the weight ofthe colloided smokeless powder pellet was about 18 grains. The pelletand initiator were loaded into a shotshell in a manner shown in FIG. 3.Upon application of electrical energy from the aforementioned powersupply and electrode, the initiator functioned to ignite the main chargeof propellant in a manner which yielded the pressure-time relationshipand shot velocity expected of a shotshell.

EXAMPLE VII A shotshell was construced in accordance with.Example VIexcept that lead peroxide was used in place of the graphite film. Thelead peroxide film was about 2 mils in thickness and showed, with theelectrode employed, had bridge resistance of about to ohms. Uponapplication of electrical energy as in Example VI, the initiatorfunctioned to satisfactorily ignite the main charge of propellant.

EXAMPLE VIII A pellet was fabricated from virgin, fibrous,nongelatinized nitrocellulose (13.1 percent nitrogen) by forming arelatively loose mat or wad from a slurry of fibres and water on afilter and then compacting the relatively loose wad in a press to adensity of about 1.2 to 1.3 grams per cubic centimeter. The resultingpellet was of the same dimensions as the pellet of Example III. Agraphite film was applied to one face of the virgin nitrocellulosepellet according to the previously cited Examples. The pellet was placedin the test fixture of Example III and upon the application ofelectrical energy ignited and burned with the necessary characteristicsrequired for industrial driving tools.

EXAMPLE IX EXAMPLE X A porous pellet was fabricated by the wash-outprocess as hereinbefore described. Pellets made by this process weretreated exactly as the pellets cited in Example III and yielded the samedesired performance.

The functioning time of the conductive film initiator described in thisdisclosure is desirably short. The functioning time may be defined asthat timewhich elapses from the first application of electrical energyto the first evidence of a pressure rise caused by the burning of thepropellant body. This functioning time is between I and 2 milliseconds.the channeled It is to be understood that the initiator of the presentinvention with a suitable amount of nitrocellulose body 4 may be used byitself as a replacement for the powder charge and primer in convenitonalammunition. It may also be used alone to provide the energy to drive abullet, to drive the piston of an industrial type fastening tool or tostart a small internal combustion engine. It may be used as areplacement for the conventional primer to ignite additional propellantor to serve as a means of igniting a mass of pyrotechnic composition oras the first element in a train of explosives.

What is claimed is:

1. In combination, a propellant charge of smokeless powder having aunitary configuration, said propellant charge having a hollow therein,an initiator mounted in said hollow, said initiator comprising a body ofnitrocellulose having a surface characterized by a plurality of exposedfibres, a conductive film adhered to said surface and in intimatecontact with the exposed fibres, said film having a negative temperaturecoefficient of electrical resistivity.

2. The combination of claim I wherein said conductive film has athickness of between about 0.5 mil and 2.0 mils and a resistance ofbetween about 2 ohms and ohms.

a UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 799I 55 Dated M rch 26, 197

Inventor) Charles G. Irish Jr. Joseph W. Si lva; Raymond l Cowles It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In the list of inventors, the name Raymond Cowles has been misspelled asRaymondl. Owles.

The following parag'raphs have been omitted in Column 5 after theparagraph ending line 5 --Another application of the initiator 2 of thepresent invention is shown in Figure 6 wherein it i's'desired' toutilize the initiator 2 as a source of power for driving the piston 7001an industrial type, powderactuated driving t oo i.' The piston 70'isgenerally'mounted in a suitable barrel 72 and the fastener 7 which isdesired to be driven inserted into the muzzle end thereof. I Thenitrocellulose body of the initiator 2 is generally pellet-shaped withthe conductive fi lm 6 applied to the rearward end thereof. Theinitiator 2 is inserted into a suitable pellet chamber 76 with-theconductive film 6 being positioned so that it will be intimately vengaged by a suitable electrode 78'of the type shown in Figure 3.

A preferredelectrical circuit for providing a source of electricalenergy for ignition-of the initiator 2 is shown in Figure 7. Suchcircuit may include a suitable battery 80 having a capacitor 82 inparallel therewith. The conductive film 6 of the initiator'Z isrepresented by the resistance 8 A sui table on-off switch 86 is providedbetween the capacitor 82 and-the two electrodes 88 and 90 for firingcontrol. It is to be noted, however, that any direct current source ofequivalent power and energy may be used, The capacitances and voltagesmay be varied widely but should be so'selected that the total energyavailable for initiation is about i joule. This effect is shown in the,fol lowing table which represents Bruceton" type testing, at threevalues of capacitance, to determine the al l-fire voltage requi red.--

Signed and sealed this 17th day of December 1974.

(SEAL) Attest:

MCCOY M, GIBSON JR} c. MARSHALL DANN Attesting Officer Commissioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE CORRECTION Patent No.3,799, Datd March 26, l97

Charles G. lrish, Jr.; Joseph W. Silva; Raymond I. Cowles.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

In the l ist of inventors the name Raymond l Cowles has been misspel ledas Raymond l Owles The following two paragraphs have been omi tted inColumn 5 after the paragraph ending line 5 --Another application of theinitiator 2 of the present invention is shown in Figure 6 wherein iti'sdesired'to utilize the initiator 2 as a source of power for drivingthe piston 7001 an industrial ty e, powderactuated driving t ool. Thepiston is generally'mounted in a suitable barrel 72 and the fastener 7which is desired to be driven inserted into the muzzle end thereof. IThe nitrocellulose body of the initiator 2 is generally pellet-shapedwith the conductive film 6 applied to the rearward end thereof. Theinitiator 2 is inserted into a suitable pellet chamber 76 wi th.-theconductive fi lm 6 being positioned so that it wi l i be intimatelyengaged by a suitable electrode 7801 the type shown in Figure 3.

A preferredelectrical circuit for providing a source of electricalenergy for ignition-of the initiator 2 is shown in Figure 7. Suchcircuit may include a suitable battery 80 having a capacitor 82 inparallel therewith. The conductive film 6 of the initiator'2 isrepresented by the resistance 8 l-. Y A suitable on-ofi switch 86 isprovided between the capacitor 82 and the two electrodes 88 and 90 forfiring control. It is to be noted, however, that any di rect currentsource of equivalent power and energy may be used. The capacitances andvoltages may be varied widely but should be so selected that the totalenergy available for initiation is about i joule. This effect is shownin the following table which represents "Bruceton" type testing, atthree values of capacitance, to determine the al l-fi re voltage required.--

Signed and sealed this 17th day of December 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR; 0. MARSHALL DANN Attesting Officer" v I Commissionerof Patents

2. The combination of claim 1 wherein said conductive film has athickness of between about 0.5 mil and 2.0 mils and a resistance ofbetween about 2 ohms and 100 ohms.